1. Field of the Invention
The present invention relates to a non-single-crystal semiconductor light emitting device which is produced through using a non-single-crystal semiconductor.
2. Description of the Prior Art
Conventionally known as a non-single-crystal semiconductor light emitting device is one that comprises a first electrode, a first non-single-crystal semiconductor layer of a first conductivity type, which is formed on the first electrode and makes ohmic contact therewith, an i-type non-single-crystal semiconductor region formed on the first non-single-crystal semiconductor layer, a second non-single-crystal semiconductor layer of a second conductivity type reverse from the first conductivity type, which is formed on the i-type non-single-crystal semiconductor region, and a second electrode which is formed on the second non-sigle-crystal semiconductor layer and makes ohmic contact therewith.
In this case, the first non-single-crystal semiconductor layer, the i-type non-single-crystal semiconductor region and the second non-single-crystal semiconductor layer are doped with a dangling bond and recombination center neutralizer such as hydrogen, or halogen such as fluorine, and the i-type non-single-crystal region is formed by a single non-single-crystal semiconductor layer.
With the light emitting device of such a construction, when connecting a DC bias source of a predetermined polarity between the first and second electrode, electrons (or holes) are injected into the i-type non-single-crystal semiconductor region from the first electrode towards the second electrode, and holes (or electrons) are injected into the i-type non-single-crystal semiconductor region from the second electrode towards the first electrode layer. The electrons (or holes) injected into the i-type non-single-crystal semiconductor region from the first electrode flow towards the second electrode without being accumulated at the bottom of the conduction band (or valence band) of the single non-single-crystal semiconductor layer forming the i-type non-single-crystal semiconductor region. Similarly, the holes (or electrons) injected into the i-type non-single-crystal semiconductor region from the second electrode flow towards the first electrode layer without being accumulated at the bottom of the valence band (or conduction band) of the single non-single-crystal semiconductor layer forming the i-type non-single-crystal semiconductor region. The electrons (or holes) thus flowing in the i-type non-single-crystal semiconductor region from the first electrode towards the second one and the holes (or electrons) thus flowing from the second electrode toweards the first one are recombined with each other in the i-type non-single-crystal semiconductor region. As a result of this, light is obtained in the i-type non-single-crystal semiconductor region, and this light is emitted as the output light from the non-single-crystal semiconductor light emitting device.
With the conventional non-single-crystal semiconductor light emitting device described above, light is obtained in the i-type non-single-crystal semiconductor region, as mentioned above. The i-type non-single-crystal semiconductor region is doped with the dangling bond and recombination center neutralizer, as referred to above. In the case where the i-type non-single-crystal semiconductor region is formed of silicon (si) and the dangling bond and recombination center neutralizer is hydrogen (H), the i-type non-single-crystal semiconductor region has such an SiH structure that one hydrogen atom is combined with a bond of one silicon atom. This SiH structure does not act as a luminesence center at room temperature. When the i-type non-single-crystal semiconductor region is not doped with the dangling bond and recombination center neutralizer, no light is produced in the i-type non-single-crystal semiconductor region at room temperature, of course. Accordingly, the above-described non-single-crystal semiconductor light emitting device in which the i-type non-single-crystal semiconductor region is formed of easily available silicon (Si) has not been proposed in practice.
Further, in the conventional non-single-crystal semiconductor light emitting device, those of the electrons (or holes) injected from the first electrode which do not recombine with the holes (or electrons) but reach the second electrode are nonnegligibly large in quantity, and those of the holes (or electrons) injected from the second electrode which do not recombine with the electrons (or holes) but reach the first electrode are also nonnegligibly large in amout. This stems from the construction of the device itself and imposes severe limitations on its light emitting efficiency.
Furthermore, the prior art non-single-crystal semiconductor light emitting device has the defect that the light therefrom cannot be obtained as light close to white light even by a suitable selection of the energy band gap of the i-type non-single-crystal semiconductor layer forming the non-single-crystal semiconductor region.